The overarching goal of this project is to determine how the brain encodes biologically-relevant olfactory stimuli including identified pheromones and feeding cues. Two specific aims are addressed: first, to determine if food-related and pheromonal odorants stimulate different, non-overlapping sets of neuronal ensembles in the olfactory bulb and forebrain as visualized by c-fos activity. The second is to use postmortem DiI retrograde tracing to identify the types of olfactory receptor neurons which converge on the functionally-defined regions of the olfactory bulb mediating responses to either food or pheromones. To address the first aim, sexually mature goldfish (a leading model of vertebrate pheromone function) will be exposed to identified sex pheromones or food stimuli at relevant concentrations, sacrificed, and the neural processes stimulated by these cues visualized in both the olfactory bulb and telencephalon using in situ hybrization and an existing probe for c-fos (an intermediate early gene). Activated regions will be identified and mapped. To address the second aim, dye tracers including DiI will be placed into olfactory bulb regions that respond to these cues, and the type (ciliated, microvillous or crypt) of olfactory receptor neurons which project to these regions identified using morphological criteria as well as various molecular markers for receptors and their G proteins. [unreadable] [unreadable]